1. The Field of the Invention
The present invention generally relates to pulley systems used in connection with swimming pool covers of the type that utilize draw cords to extend and retract the cover. More particularly, the present invention is directed to a pulley assembly adapted for use with a track carrying such draw cords.
2. The Prior Art
It has been found very desirable to provide swimming pools with a removable cover which is placed over the pool when the pool is not in use. Use of such a cover greatly reduces evaporation loss and thus significantly decreases losses of thermal energy and chemicals. Use of a cover also reduces the need for filtration because the pool remains much cleaner.
Although various types of covers are available, the type of pool cover disclosed in U.S. Pat. No. 3,050,743 has met with great commercial acceptance. This type of cover typically includes a spool assembly installed at one end of the pool onto which one end of a flexible cover is secured in a manner such that the cover material may be extended and retracted along the length of a pool by rotating the spool.
The cover material is generally provided with beaded side edges formed by enclosing a draw cord within a marginal fold on each side of the cover. Each draw cord typically extends from the end of the cover, passes around a pulley at the end of the pool opposite the location of the spool assembly, and returns to a take up reel located near the spool assembly. An extruded track having a channel for guiding the beaded side edge and draw cord is generally secured to each side of the pool; the track also has a second channel for the returning end of the draw cord. In use, the reels are rotated so as to collect the draw cords thereon, thus causing the cover to be extended over the pool. For retraction, the spool is rotated in the opposite direction so as to rewind the cover.
In the past, one approach for mounting the pulley at the end of the pool opposite the spool assembly and reels has been to secure the pulley to the pool deck at a position beyond the end of the track. However, it is undesirable to utilize an exposed pulley because such an arrangement is unattractive and presents various safety hazards. Additionally, the use of an exposed pulley increases maintenance as it is necessary to keep the pulley clean and free of debris in order for it to function properly.
Because of these disadvantages, the conventional approach has been to mill out a portion of the track sufficiently so as to accommodate placement of a pulley. When this approach has been taken, the end of the track has typically been capped in order to seal off the exposed track channels. FIG. 1 illustrates such a prior art approach wherein a pulley 10 is secured near the end of a milled-out section 12 of a conventional track 14, with the exposed end of the track being fitted with an end cap 16. This is the approach disclosed in U.S. Pat. No. 3,051,232.
Placement of a pulley within a milled-out portion of the track has been acceptable from the standpoint of mechanical operation and this has been a standard practice for many years. However, this approach requires that a special milling step be performed during manufacture in order to prepare the extruded track so that the pulley may be attached thereto. In addition to the extra time involved to perform this milling step, the conventional approach also requires special tooling and skilled manpower. Additionally, it is not uncommon to remove too much material during the milling step. When such a mistake is made, or if the milling step is otherwise performed incorrectly, the end of the section of track must be cut off and discarded, and the milling step repeated. These factors all result in significantly greater costs attributable to the conventional placement of the pulley within a milled-out portion of the track.
Yet another disadvantage of the practice of securing a pulley within a milled-out portion of the extruded track is that the pulley is quite inaccessible once the track is secured in place to the pool deck since access to the pulley is only possible from the underside of the track. If for any reason the installer or a serviceman needs access to the pulley, it is necessary to detach the track from the pool deck sufficiently so that the track may be lifted, thereby giving access to the pulley. This significantly increases the cost of service and maintenance on an installed pool cover.
Yet another disadvantage of the conventional practice of placing a pulley within a milled-out portion of the track is that there is typically a large gap between the pulley and various surfaces of the track. This often results in disengagement of the draw cord from the pulley when slack is introduced or permitted to develop in the draw cord, which in turn frequently results in binding of the draw cord and rough operation of the pulley.
From the foregoing, it will be readily appreciated that it would be a significant advancement in the field of pool covers of the general type described above to provide for the installation of a pulley in connection with a section of extruded track that would avoid the need for milling out a portion of the track, and yet would allow use of an enclosed draw cord and pulley system. It would also be a significant advancement to provide for ready access to the pulley without the need to dismantle and remove the track assembly from its installed position. It would also be a significant advancement to provide for the installation of a pulley in a manner that would prevent disengagement of the draw cord so as to insure smooth operation and so as to prevent binding. The invention which is disclosed and claimed herein meets these longstanding needs.